A fundamental model for prediction of optimal particulate composite properties

Particulate composite systems comprising a high content of granular filler (over 60% by weight) in a polymer matrix are greatly influenced by the filler-to-binder ratio, the size distribution of the filler particles and the amount of wetting and adhesion between the filler and the matrix. Relative density and mechanical compressive properties present sensitive variables for studying these effects. Two principal models are presented, one for evaluating the optimal filler size distribution (gradation) and the other to determine the optimal matrix content for this evaluated gradation. Adopting both models provides a prediction of a composite system with enhanced mechanical properties and optimal compaction. The constants of both models are derived experimentally using an epoxy/SiC mixture. The optimal distribution of the matrix between the various filler components and the optimal filler gradation of the composite system are thus obtained. Results show that, despite its low content, the fine filler plays a major role in determining the total optimal composite mixture. Slightly different constants are determined for the various properties tested. Optimal formulation can thus be specified for either a critical property desired or a mean optimum for all relevant properties. Experimental verification of both models proves their efficiency in predicting optimal mixture parameters in order to achieve the best performance of the polymerized composite system.